Convertible Senior Notes (Tables)

9 Months Ended

Sep. 30, 2019

Debt Disclosure [Abstract]

Schedule of Components of Convertible Senior Notes

The Notes consist of the following (in thousands):

	As of September 30, 2019			As of December 31, 2018
Liability component:
Principal	$	115,000		$	115,000
Less: debt discount, net of amortization		(17,236	)		(20,903	)
Net carrying amount	$	97,764		$	94,097
Equity component (1)		22,094			22,094

⁽¹⁾ Recorded in the consolidated balance sheet within additional paid-in capital, net of $0.8 million transaction costs in equity as of December 31, 2017.

Summary of Total Interest Expense Recognized Related To Convertible Senior Notes

The following table sets forth total interest expense recognized related to the Notes (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
1.50% coupon	$	429	$	432	$	1,294	$	1,301
Amortization of debt discount and transaction costs		1,243		1,160		3,667		3,435
	$	1,672	$	1,592	$	4,961	$	4,736

Summary of Fair Value and Carrying Value of Convertible Senior Notes

As of September 30, 2019 and December 31, 2018, the fair value of the Notes, which was determined based on inputs that are observable in the market or that could be derived from, or corroborated with, observable market data, quoted price of the Notes in an over-the-counter market (Level 2), and carrying value of debt instruments (carrying value excludes the equity component of the Company’s convertible notes classified in equity) were as follows (in thousands):

	As of September 30, 2019				As of December 31, 2018
	Fair Value		Carrying Value		Fair Value		Carrying Value
Convertible senior notes	$	217,947	$	97,764	$	189,802	$	94,097